PVE is fun, rewards for free players are good too (10 gold per day and an additional 30 per week if you play in arena for a certain amount of games).

However, PVP is still pay to win (Taiwanese version of this game was released 6 months ago, and there are next to no free players in 1v1 ladder). Almost every card free player uses has a legendary (5*) or godlike (6*) version, so even if both players use the same card, the one with higher rarity usually has an advantage.